French Patent Application No. 2,598,975 describes apparatus for opening envelopes and including:
a conveyor for feeding the envelopes along a horizontal slideway, the fold of each envelope sliding along this slideway;
rollers for extracting an envelope from the slideway along a vertical path;
a fixed blade, parallel to the axes of the rollers, and co-operating with the rollers to arch the body of an envelope without arching the flap, so as to create a space between the body and the flap, the blade then being inserted into the space and pivoting the flap through 180.degree. by means of the envelope moving in translation relative to the blade; and
means for carrying an envelope away while keeping it open, after it leaves the rollers.
That apparatus has several drawbacks. The motion of each envelope is discontinuous since the envelope arrives horizontally and leaves vertically. The operation of the rollers is also discontinuous. One of them is mounted on a pivoting arm having a rest position in which the rollers are spaced apart to enable an envelope to arrive, and a work position in which the rollers are clamped together and turn so as to drive the envelope. These discontinuities of motion limit the rate of operation of that apparatus.
When separating the flap from the body of the envelope and pivoting the flap through 180.degree., the blade acts very suddenly because it comes up against the inside of the fold connecting the flap to the body of the envelope, before the flap starts to pivot.
Furthermore, that known apparatus is sensitive to the presence of accidental points of adhesion between the flap and the body of an envelope. At the moment when the blade is inserted between the flap and the body of the envelope, there is a risk that the flap will tear, thereby jamming the apparatus.
That apparatus has to be adjusted for each type of envelope, because the position of the envelope relative to the blade must be such that the blade is inserted properly under the flap, and such that the rollers pinch the envelope without pinching the flap. If the envelope is smaller, the two rollers might not be able to extract it from the slideway. If the envelope is larger, the end of the flap might extend beyond the end of the blade. In this case, the blade cannot be inserted between the flap and the body of the envelope. The position of the end of the blade must also be adjusted as a function of the thicknesses of the envelopes to be opened. In order for that prior apparatus to operate correctly, accurate adjustment is therefore necessary, as a function of the sizes of the envelopes and of their flaps.
The fact that open envelopes leave that apparatus in a direction perpendicular to the arrival direction of envelopes to be opened complicates integrating the apparatus into a mail handling machine, because it cannot be integrated into a conventional conveying station in which the envelopes follow a constant direction.
An object of the invention is to provide apparatus which does not suffer from the drawbacks of that known apparatus.